{ x1 = k7 + piecewise(k8, t <= k15, 0) + k9*t/k16, 1*k17*x4 + 1*k17*x5 + 1*k17*x6 + 1*k17*x8 = k17*k30, 1*k17*x7 + 1*k17*x8 + 1*k17*x9 = k17*k31 }